Polymers of conjugated dienes, such as butadiene, or copolymers of conjugated dienes with one or more monovinyl-substituted aromatic hydrocarbons, such as styrene, are widely employed as synthetic elastomeric composition in a variety of applications. Recently, there has been considerable interest in preparing normally liquid polymers, and then curing to a firm gum stock with various curing agents. However, the nature of such stocks, and the ability to make a good cured stock, depends on a number of factors. If a convenient but highly functional liquid polymer could be prepared with a sufficiently high functionality that it could be readily cured to a tight stock, then a true castable rubber would be at hand, simplifying much processing, and open many product applications in forming polymeric products.
In prior art processes, some functionality, of course, has been provided in polymers by converting lithium end groups of a lithium-initiated solution-polymerized polymer to hydroxyl groups. A linear polymer, for example, thus would contain about 1-2 hydroxyl groups per polymer molecule depending on initiation with mono- or dilithio initiators. However, while these limited hydroxyl groups are useful in curing with a variety of curing agents, nevertheless, the quite limited functionality normally available has been a limiting factor in trying to produce a truly castable rubber.